Minimal-flow Anesthesia and Cognitive Outcomes in Elderly Surgical Patients

March 16, 2026 updated by: oya Çimen, Ankara Etlik City Hospital

Minimal-flow Anesthesia, Surgical Duration, and Postoperative Cognitive Dysfunction in Older Patients

Purpose:

Postoperative cognitive dysfunction (POCD) is a common complication in elderly patients following major surgery and is associated with impaired attention, memory, and executive functions. Advanced age and prolonged surgical duration are among the most important risk factors. Minimal flow anesthesia has been suggested to reduce postoperative cognitive impairment by providing more stable anesthetic depth and reducing physiological stress.

The aim of this study is to investigate the relationship between surgical duration and postoperative cognitive dysfunction in elderly patients undergoing surgery under minimal flow anesthesia.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

Detailed Description:

Postoperative cognitive dysfunction (POCD) is a syndrome characterized by deterioration in cognitive domains such as attention, memory, executive function, and psychomotor speed, particularly in elderly patients after major surgical procedures. POCD may become evident in the early postoperative hours or may present days to weeks after surgery. Its incidence increases with age, prolonged surgical duration, anesthetic technique, comorbid conditions, and perioperative physiological disturbances.

Diagnosis of POCD requires comparison of preoperative baseline cognitive status with postoperative neurocognitive assessments. The Mini-Mental State Examination (MMSE) and the Richmond Agitation-Sedation Scale (RASS) are validated and reliable tools for evaluating cognitive status in the perioperative period.

Minimal flow anesthesia is defined as the use of fresh gas flow rates between 0.25 and 0.5 L/min, allowing partial rebreathing of anesthetic agents. This technique reduces anesthetic consumption, maintains stable anesthetic depth, and preserves temperature and humidity, potentially minimizing physiological stress. Previous studies suggest that minimal flow anesthesia with sevoflurane may be associated with a lower incidence of early postoperative cognitive impairment compared to higher flow techniques.

In this prospective interventional study, patients aged 65-85 years undergoing surgery under minimal flow inhalational anesthesia will be enrolled. Patients will be divided into two groups based on surgical duration: surgeries lasting less than 2 hours and surgeries lasting 2 hours or longer, with 45 patients in each group.

All patients will undergo preoperative cognitive assessment using the MMSE. Standard ASA monitoring and bispectral index (BIS) monitoring will be applied intraoperatively to maintain anesthetic depth between BIS values of 40 and 60. Anesthesia induction and maintenance will be performed using routine anesthetic agents and minimal flow inhalational anesthesia as part of standard clinical practice.

Neuromuscular blockade will be reversed with sugammadex at the end of surgery. Postoperatively, patients will be evaluated using the RASS at the 10th, 30th, and 60th minutes in the recovery room. Neurology consultation will be requested for patients with RASS scores outside the normal range. Vital signs, pain scores (VAS), and blood glucose levels will be recorded during these assessments.

Postoperative cognitive function will be reassessed using the MMSE at 24 hours and on postoperative day 7. Preoperative and postoperative cognitive assessments will be conducted by study investigators who are blinded to surgical duration. The anesthetic management will be performed by anesthesiologists not involved in the study.

The primary objective of this study is to evaluate the association between surgical duration and postoperative cognitive dysfunction in elderly patients undergoing surgery under minimal flow anesthesia.

Study Type

Interventional

Enrollment (Actual)

90

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Turkey (Türkiye)
    • Ankara
      • Yenimahalle, Ankara, Turkey (Türkiye), 06170
        • Ankara Etlik City Hospital

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:Inclusion Criteria:

  • Patients aged between 65 and 85 years
  • ASA physical status I-III
  • Scheduled for elective surgery under general anesthesia in general surgery or otorhinolaryngology operating rooms
  • Planned to receive minimal flow general anesthesia
  • Preoperative Mini-Mental State Examination performed
  • Able to provide informed consent

Exclusion Criteria:

  • Age outside the specified range
  • ASA physical status IV or higher
  • Severe comorbid disease affecting perioperative stability
  • Surgery performed under regional anesthesia
  • History of alcohol, drug, or substance abuse
  • Significant visual or hearing impairment interfering with cognitive testing
  • Refusal to participate
  • Known neurological or psychiatric disorders
  • Preoperative MMSE score below 24
  • Perioperative hemodynamic instability
  • Illiteracy preventing completion of cognitive tests
  • Postoperative admission to intensive care unit

Exclusion Criteria:

-

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Other
  • Allocation: Non-Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Arm 1: Surgery duration <2 hours
Elderly patients undergoing surgery under minimal flow anesthesia with a surgical duration of less than 2 hours. Cognitive function will be assessed preoperatively and postoperatively using the Mini-Mental State Examination.
Other: Mini-Mental State Examination
Cognitive function will be assessed using the Mini-Mental State Examination preoperatively and at postoperative time points.
Other Names:
  • MMSE
Experimental: Arm 2: Surgery duration ≥2 hours
Elderly patients undergoing surgery under minimal flow anesthesia with a surgical duration of 2 hours or longer. Cognitive function will be assessed preoperatively and postoperatively using the Mini-Mental State Examination.
Other: Mini-Mental State Examination
Cognitive function will be assessed using the Mini-Mental State Examination preoperatively and at postoperative time points.
Other Names:
  • MMSE

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in Mini-Mental State Examination score
Time Frame: Preoperative baseline, postoperative 24 hours, and postoperative day 7

Cognitive function will be assessed using the Mini-Mental State Examination (MMSE), a 30-point scale ranging from 0 to 30, where higher scores indicate better cognitive function. The primary outcome is the change in MMSE score between the preoperative assessment and postoperative assessments.

Change in cognitive function assessed by the difference between preoperative and postoperative Mini-Mental State Examination scores.
Preoperative baseline, postoperative 24 hours, and postoperative day 7

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Incidence of postoperative cognitive dysfunction
Time Frame: Postoperative 24 hours and postoperative day 7
The proportion of patients who develop postoperative cognitive dysfunction based on changes in Mini-Mental State Examination (MMSE) scores. Postoperative cognitive dysfunction will be defined according to a predefined decline in MMSE score compared with the preoperative baseline assessment.
Postoperative 24 hours and postoperative day 7

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Ankara Etlik City Hospital

Investigators

  • Principal Investigator: oya çimen, MD, Ankara Etlik City Hospital

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

October 3, 2025

Primary Completion (Actual)

March 12, 2026

Study Completion (Actual)

March 15, 2026

Study Registration Dates

First Submitted

February 5, 2026

First Submitted That Met QC Criteria

February 18, 2026

First Posted (Actual)

February 20, 2026

Study Record Updates

Last Update Posted (Actual)

March 18, 2026

Last Update Submitted That Met QC Criteria

March 16, 2026

Last Verified

March 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • AEŞH-EK-2025-187

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data will not be shared because the study involves a single-center academic dataset and no data-sharing agreement has been established. De-identified data may be made available upon reasonable request to the principal investigator.

Study Data/Documents

  1. Study Protocol
    Information comments: The study protocol and individual participant data will not be publicly available. No data sharing is planned for this study and no access to datasets or documents will be provided.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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